The aim of the proposed project is the study of two aspects of neonatal adrenal function. First, the usefulness and validity of serum dehydroepiandrosterone sulfate (DHAS) as a steroid markkr of adrenocortical fetal zone activity will be assessed. Serum DHAS and cortisol levels will be followed serially in hospitalized normal newborn infants and in infants with intrauterine growth retardation (IUGR), and responses of these two steroids to ACTH stimulation will be measured. As infants with IUGR have smaller than normal fetal zones, these infants can be used as experiments of nature in answering the question about the validity of DHAS as a steroid marker of fetal zone function. The second aim of the proposed project is to determine the normalcy of neonatal adrenal function in infants born after gestations of more than 42 weeks, and particularly, the adequacy of adrenocortical function in infants with he postmaturity syndrome. The plan is to correlate certain measures of adrenal function, serum cortisol and DHAS in umbilical serum before and after ACTH administration, with clinical signs of postmaturity in the post-term infants. The maternal serum DHAS and estradiol-17 Beta responses to I.V. loads of unlabelled DHAS will be evaluated in post-term pregnancies (greater than 42 weeks) as a means of diagnosing placental insufficiency severe enough to result in postmaturity syndrome in the fetus and neonate.